LOS ANGELES (June 26, 2009)—After a three-hour autopsy Friday, a spokesman for the Los Angeles County Coroner’s Office said a final ruling on the cause of the death of pop superstar Michael Jackson won’t be released for four to six weeks.

That’s how long it will take to complete toxicology tests.

Spokesman Craig Harvey did say there was no indication of external trauma or foul play, however.

He also said Jackson was taking some unspecified prescription medications.

The Los Angeles Police Department has placed a security hold on the case, which means only limited information about the death may be released, he said.

Earlier Friday, the Los Angeles Fire Department released a tape of the 911 call from Jackson’s home in which a caller says the singer wasn’t breathing or responding to resuscitation attempts.

The unidentified caller said Jackson was with his personal doctor at the time.

The doctor was later identified as Dr. Conrad Robert Murray, a cardiologist licensed to practice in Texas and Nevada who has a clinic in Houston.

A woman who answered the phone Friday at Murray's clinic in Houston confirmed to The Associated Press that Murray was Jackson's cardiologist.

The woman, who refused to give her name, would not confirm a Los Angeles Times report that Murray was performing CPR on Jackson when paramedics arrived at the entertainer's home Thursday.

The Texas State Board of Medical Examiners Web site shows no complaints filed against Murray in the four years he's been a licensed cardiologist in Texas.

Los Angeles police spokeswoman Karen Rayner said Friday police towed a BMW that Murray was using from Jackson’s house because it may contain evidence to help determine the cause of the singer’s death.

"We have not been able to interview the doctor yet. His car was impounded because it may contain medications or other evidence that may assist the coroner in determining the cause of death,” Rayner said.

The car has Texas license plates and is registered to Murray’s sister.

TMZ.com earlier reported that the doctor lived at the home.

Jackson died Thursday at UCLA Medical Center after he collapsed at home.

Paramedics tried to resuscitate him for nearly three-quarters of an hour, then rushed him to the hospital, where doctors continued to work on him for an hour, according to a Jackson family statement.

His brother Jermaine says "It is believed he suffered cardiac arrest in his home."

However, he says, ”The cause of his death is unknown until results of the autopsy are known."

Jackson, who was 50, was preparing for what would have been a series of 50 concerts starting July 13 in London.

Meanwhile Friday, accolades continued to pour in.

Musician Quincy Jones, who produced Jackson's "Thriller" says the pop star "was the consummate entertainer" and he says "his contributions and legacy will be felt upon the world forever."

Across the country, people have reacted in stunned disbelief.

At Times Square in New York, a collective groan went up from the crowd as word of his death flashed across a giant TV screen.

One man says he cried when he heard the news.

He said he thought Jackson was "immortal."

Among Jackson's fellow performers, Wyclef Jean called Jackson his "musical god," while Celine Dion said Jackson was her "idol."

Dick Clark knew Jackson from his childhood when he started in the Jackson 5.

Clark said of all the entertainers he's worked with, Jackson was "the most outstanding."

Fans camped out through the night along with media outside the Jackson family house in California's San Fernando Valley, and near his star on the Hollywood Walk of Fame.